Re: Ice cream scoops

[Sam Held <held@utkux.utcc.utk.edu>]

Leigh,
	Sorry, but I goofed.  I hope that people did realize the very
obvious mistake that the melting point should be above 0 Celsius.  You
want something similar to salting roads during snow storms, you effect the
freezing point.  So this liquid should have a large specific heat such
that they don't give up their heat very easily.  I am surprised you have
never seen these scoops before.  Try going to the local ice cream stand
and see if their scoops swish when you shake them.  They sell them at
the supermarket here and in specialty cooking stores in the mall.


							Sam Held
sheld@utk.edu

On Tue, 9 Jun 1998, Leigh Palmer wrote:

> > 	I think they use some type of glycerol or something (I started
> > in chemical engineering and knew this at one point) like it with a
> > freezing point below 0 Celius that helps keep the scoop warm.  Because as
> > Leigh pointed out, solid metal scoops stick to the ice cream.
>
> One wants a freezing point *above* the freezing (or sticking) point
> of the ice cream, not below it. The reason is straightforward*. As
> the scoop cools it will eventually reach the freezing point of the
> liquid it contains. Further use of the scoop will not cool it
> appreciably until all the liquid is frozen. The latent heat of
> freezing must be extracted before further cooling is possible. Thus
> it is desirable to have a liquid with a freezing point at the
> desired operating temperature, and with a latent heat as large as
> practical, consistent with keeping the mass and volume small. Water
> is the obvious choice for this substance, which is why I guessed it.
>
> Ludwik, I've never heard of such an ice cream scoop before. It is a
> clever idea. Where does one obtain this device? What is it called?
> The patent may be available on the web, and I would like to see it.
>
> Leigh
>
> *When I say "straightforward" I am making a statement about the
> manner in which I speak about the physics here. As Jim Green will
> recognize I employ the caloric model in this discussion. In that
> model heat is considered to be a substance which flows from one
> place to another. This pedagogical point I only raise here because
> I am now writing a short paper on just this topic which I hope will
> be accepted for publication by The Physics Teacher.